iOS: Custom transitioningDelegate doesn't work - ios

Question

This is my custom transitioningDelegate:
enum CameraState {
case On
case Off
}
class CameraTransitioning: NSObject, UIViewControllerAnimatedTransitioning, UIViewControllerTransitioningDelegate {
var state: CameraState
init(state: CameraState) {
self.state = state
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
let containerView = transitionContext.containerView()
let fromVC = transitionContext.viewControllerForKey(UITransitionContextFromViewControllerKey)
let toVC = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)
let fromView = transitionContext.viewForKey(UITransitionContextFromViewKey)
let toView = transitionContext.viewForKey(UITransitionContextToViewKey)
var toViewInitialFrame = transitionContext.initialFrameForViewController(toVC!)
var fromViewFinalFrame = transitionContext.finalFrameForViewController(fromVC!)
switch self.state {
case .On:
toViewInitialFrame.origin.y = containerView!.frame.height
case .Off:
fromViewFinalFrame.origin.y = -containerView!.frame.height
}
containerView?.addSubview(toView!)
toView?.frame = toViewInitialFrame
let duration = self.transitionDuration(transitionContext)
UIView.animateWithDuration(duration, animations: {
fromView?.frame = fromViewFinalFrame
}) {
finished in
transitionContext.completeTransition(true)
}
}
func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
return 10
}
func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return self
}
func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return self
}
}
And this is how I use it:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "Home -> Camera" {
let cameraVC = segue.destinationViewController as! CameraViewController
cameraVC.delegate = self
cameraVC.transitioningDelegate = CameraTransitioning(state: .On)
}
}
As you can see, I use this transitioning because I don't like the default UIViewAnimationCurveEaseInOut, and I have tried to set the duration to 10 to make this change clear. But this doesn't work. Where is the problem?

Answer 1

The transitioningDelegate property is weak, and you are creating no other strong references to it. Something else needs to own that object for it to stick around long enough to be used to animate the transition.